不同于4B上的BCM2711，外设扩展用的是第三方的芯片VL805，在BCM2712上树莓派采用了一款自主设计的RP1接口芯片，下面我们来看一下关于RP1的描述：
RP1

Previous Raspberry Pi generations were built on a monolithic AP architecture: while some peripheral functions were provided by an external device (the Via Labs VL805 USB controller and hub on Raspberry Pi 4, and the Microchip LAN951x and LAN7515 USB hub and Ethernet controller chips on earlier products), substantially all of the I/O functions were integrated into the AP itself. Fairly early in the history of Raspberry Pi, we realised that as we migrated the AP to progressively newer process nodes, this approach would eventually become both technically and economically unsustainable.

Raspberry Pi 5, in contrast, is built on a disaggregated chiplet architecture. Here, only the major fast digital functions, the SD card interface (for board layout reasons), and the very fastest interfaces (SDRAM, HDMI, and PCI Express) are provided by the AP. All other I/O functions are offloaded to a separate I/O controller, implemented on an older, cheaper process node, and connected to the AP via PCI Express.

RP1 is our I/O controller for Raspberry Pi 5, designed by the same team at Raspberry Pi that delivered the RP2040 microcontroller, and implemented, like RP2040, on TSMC’s mature 40LP process. It provides two USB 3.0 and two USB 2.0 interfaces; a Gigabit Ethernet controller; two four-lane MIPI transceivers for camera and display; analogue video output; 3.3V general-purpose I/O (GPIO); and the usual collection of GPIO-multiplexed low-speed interfaces (UART, SPI, I2C, I2S, and PWM). A four-lane PCI Express 2.0 interface provides a 16Gb/s link back to BCM2712.

Under development since 2016, RP1 is by a good margin the longest-running, most complex, and (at $15 million) most expensive program we’ve ever undertaken here at Raspberry Pi. It has undergone substantial evolution over the years, as our projected requirements have changed: the C0 step used on Raspberry Pi 5 is the third major revision of the silicon. And while its interfaces differ in fine detail from those of BCM2711, they have been designed to be very similar from a functional perspective, ensuring a high degree of compatibility with earlier Raspberry Pi devices.